Digital monitoring of disease activity in relapsing-remitting multiple sclerosis

Digital monitoring shows promise for detecting disease activity in people with relapsing-remitting multiple sclerosis (PwRRMS). Here, we study associations between digital biomarkers for cognition and walking ability and radiological disease activity.

In a prospective, 1-year cohort study, PwRRMS performed the smartphone-based symbol digit modalities test (sSDMT) and 2-min walk test (s2MWT) on weekly basis. MRIs and the clinical SDMT (cSDMT), expanded disability status scale (EDSS), timed 25-foot walk (T25FW) and nine-hole peg test (NHPT) were collected at baseline and every 3 months. Associations were determined using logistic generalized estimating equations. For the digital measures, associations were also analyzed using a hybrid model and were repeated with values from 6 weeks before and after MRI.

We included 57 PwRRMS. The sSDMT was negatively associated with contrast-enhancing lesions (CELs) (OR_overall 1.80, 95% CI 1.12-2.91), predominantly caused by variation within individuals (OR_{within-subjects} 4.37, 2.05-9.33), with a similar relation using sSDMT values 6 weeks prior to MRI (OR_overall: 1.92, 0.947-3.90, OR_{within-subjects}: 13.7, 1.74-107). The negative association between s2MWT and CELs (OR_overall 1.20, 1.04-1.38) was caused equally by variation within and between individuals. All clinical measures were negatively associated with CELs: T25FW (OR_overall 2.23, 1.50-3.32), EDSS (OR_overall 1.49, 0.932-2.39), cSDMT (OR_overall 1.20, 1.02-1.42) and NHPT (OR_overall 1.15, 1.04-1.27).

Digital biomarkers show to be capable of measuring changes in individuals when inflammation is detectable on MRI, with the sSDMT additionally capturing changes 6 weeks prior to the MRI, suggesting that early identification of inflammation using these biomarkers may be possible.